An apparatus is disclosed for preparing a solution of a solid with a liquid and/or for diluting a liquid with a further liquid by means of a balance and at least one electronic dosage delivery device for liquids, in particular an electronic pipette, where the arrangement includes a means of communication between the balance and the at least one electronic dosage delivery device. A method involving the use of the apparatus for preparing solutions and/or dilutions in a laboratory is also disclosed, as is a program through which the apparatus carries out the method.
Dosage delivery devices, in particular hand-held electronic dosage delivery devices such as electronic pipettes, burettes, and other dispensers, are widely used in laboratories. Applications for such devices are found in all processes where a defined quantity of a liquid has to be added, for example in the preparation of solutions or dilutions. In most cases, the devices are used for routine laboratory procedures where a wide diversity of different end products are to be produced with different chemicals, but where such procedures usually occur one at a time, i.e., not frequently enough that, e.g., the use of a laboratory robot could be economically justified. Nevertheless, it is desirable to simplify and automate electronic dosage delivery systems and thereby improve the ways in which operational procedures, operating parameters, and programs or program parts can be influenced and controlled and to provide better assurance of the resulting data.
The European Patent Application EP 0 999 432 A1 describes a method of operating an electronic dosage delivery system and also describes a dosage delivery system of the kind envisaged by the method, with a handheld electronic dosage delivery device such as, e.g., an electronic pipette with a data interface through which a communication to the data interface of a data processing system can be implemented by way of an electronic data transfer connection. The data communication provides read/write access from the data processing system to a memory of the handheld dosage delivery device, so that memory parameters specific to the instrument type and/or to the individual instrument and/or to the application, and/or program routines for application procedures and/or the program of the controller device of the handheld electronic dosage delivery device and/or at least a program part can be written into or read out from the memory of the handheld dosage delivery device, and/or the handheld dosage delivery device can be remote-controlled. Remote control of the dosage delivery device is advantageous for dosage-dispensing procedures, e.g., if the handheld dosage delivery device is used within a superordinate automation process, or to use the handheld dosage delivery device in a contaminated environment without endangering the person attending to the process. By means of a program routine for running application procedures, it is possible, e.g., to control the intake, mixing, and dispensing of defined quantities of liquid, or to carry out a sequence of diluting steps, where the dispensed dosage volume is halved in each successive step. As a further possibility, an application routine of this kind can also be transferred into the handheld dosage delivery device.
Besides electronic dosage delivery devices for liquids, in particular handheld devices such as pipettes or dispensers, routines for preparing solutions and/or dilutions in the laboratory also involve the use of electronic balances. For example in the case of preparing a solution, the first step is weighing-in a defined quantity of a solid substance into a container on the balance. Based on a desired concentration of the solution, one calculates the quantity of the liquid solvent that needs to be added, e.g., by means of a pipette or a measuring cylinder or an other container. It needs to be noted, however, that in order to obtain a desired end result, this procedure requires a sufficiently accurate accounting for parameters of the liquid solvent such as temperature, density, coefficient of volume expansion and/or purity of the solvent. As a rule, the person who was given the task of preparing the solution and/or dilution makes these calculations by means of a simple laboratory computer or pocket calculator. In most cases, a calculation of this kind is time-consuming and entails the risk of calculation errors. Furthermore, there is no control mechanism to check whether the resulting solution and/or dilution is plausible in view of the data entered into the calculations and to what extent the end product lies within the target range of the desired concentration.
It is also common practice to prepare a quantity of solution that matches the available container. This means that in preparing a solution, e.g., in a measuring flask of a given volume, the substance quantities entering into the solution have to be calculated and weighed in under the constraint that the volume of the measuring flask determines the volume of the solution or dilution to be prepared. Often, this has the consequence that an excess quantity of solution is prepared which, if it is not otherwise needed, has to be safely disposed of.
The International PCT Application WO 02/073142 A1 describes an apparatus for mixing substances, in particular dyestuff components, which includes units that are integrated in a measuring device—in particular in a balance—such as a processor unit, a local memory unit for the storing of mix formulas, a display unit and an input unit. The balance measures the quantities of component substances that are added to a container sitting on the balance pan. In the case of an automated process, the balance controls valves that are connected to supply conduits, in accordance with the relative proportions of the substances to be mixed. The actual weight measured by the balance is continuously compared to a target value that is based on a mixture formula, and the result of the comparison is used to control the inflow of the substance that is to be added to the container.
The European Patent Application EP 0 651 306 A1 discloses an apparatus for preparing solutions, where a container that is to receive the components of a solution is resting on the pan of a balance. The solvent liquid is added through a valve connected to a conduit through which the solvent is supplied from a solvent reservoir by means of a pump. The valve and the pump as well as the balances are monitored by a control unit. Based on a procedure stored in the control unit, an indication of limit values in the form of weight values for the addition of solvent are presented to the individual attending the apparatus. Based on the weight data delivered by the balance, which are graphically presented in the form of moving bar in an output unit, the attendant is guided to stop the inflow of solvent when the weight value is within the indicated limits.
The International PCT Application WO 83/02761 A1 likewise discloses an apparatus for the preparation of solutions, where a control unit and a balance belong to the apparatus and where the solvent liquid is added through valves connected to a conduit through which the solvent is supplied from a solvent reservoir by means of a pump. The delivery of the desired quantity of solvent occurs manually or automatically in accordance with a control program, as the measured weight values are continuously transferred to the control unit and indicated on an output unit. The valves have different flow rates, so that at the beginning of a solvent delivery the valve with the higher flow rate is opened and as the weight value for the total weight of the solution approaches its target value, the valve with the lower flow rate is used for the end of the solvent delivery.
The aforementioned references disclose methods of preparing a mixture or a solution where the delivered dose of the solvent or an additional component is controlled through a comparison of an actual value to a target value in an arrangement with a substantially fixed installation of the means for delivering the dosage quantities.